Patients in unstable or critical medical condition often require continuous vital sign monitoring. This includes hospitalized patients in ICUs, internal medicine, cardiology, surgery, etc. Similarly, patients in nursing homes or their own home may need to be monitored. The data gathered by the monitoring system is often relayed to a local display and analysis, remote display and analysis (in locations such as a nursing home, a telemedicine center, etc). Various alarms may also be activated by the data which may be analyzed on-line or off-line.
In practice, in the non-ICU environment, the main parameter monitored is the ECG, often with the addition of respiration, blood oxygen saturation level, and blood pressure. However, the information that these parameters provide regarding the clinical state of the patient is limited, and the patient may fall into a dangerously critical situation without the monitor providing in a sufficiently early time reliable warning signs or alarms. This failure may be due to the fact that the information provided by the ECG is mainly related to arrhythmias and in some cases to significant cardiac ischemia, and the information provided by the O2 saturation is also limited to severe cardio-pulmonary failure. As a result, other dangerous conditions may go undetected.